A script to render each frame as image (not render animation) in 2.8
The solution is to use a script to render each frame, and the script needs to include a short time pause.
This is the script that solved the problem I have had for days.

import bpy
import time

scene = bpy.context.scene
for frame in range(scene.frame_start, scene.frame_end + 1):
    scene.render.filepath = 'C:/blndtmp/' + str(frame).zfill(4)
    scene.frame_set(frame)
    bpy.ops.render.render(write_still=True)
    time.sleep(3)


Thankyou for all your help Blender Community :)